Are you 100% sure you did this?
1. Prepare DNS
Create a wildcard A record pointing to the public IP of your VM. As an example, *.netmaker.example.com. Alternatively, create records for these specific subdomains:
dashboard.domain
api.domain
broker.domain
Ping all the domains and check if they resolve the right IP.
You can try again with the quick install where there is a domain genereated for you.